Graduate student Xiaofei Ye (left) helps postdoctoral scholar Liming Zhang adjust an experimental device that, confounding conventional wisdom, showed that heating metal oxide solar cells increased their efficiency. Credit Tom Abate

A team of engineers from Stanford University made a discovery involving ordinary metal oxides (such as rust) and more efficient solar cells. In short, these oxides can be used to make better solar cells.

The impact of this discovery

It is known fact that, sooner or later, we will run out of fossil fuel. Scientists all over the world have been working hard to come up with new (and more sustainable) sources of energy. We also need to consider the alarming state of our planet, as global warming isn't really getting any better.

Solar energy is limitless, but there are obstacles hindering its widespread use. For example, we still need to come up with ways of storing this energy and obtaining power if the Sun's not shining.

With that in mind, engineers need to make this limitless solar power "dispatchable," which means we need to be able to control the power output or hold it back, depending on the demand.

How it works

The discovery focuses solar cells that can split water into hydrogen and oxygen. By doing this, the energy is stored during the day and can be fully utilized at night. The photons captured by the cell are converted into electrons, which then provides the energy to split the water. At night, hydrogen and oxygen are put back together, which reclaims the energy gathered during the day without compromising any fossil fuels or releasing more carbon into our planet's atmosphere.

In the journal Energy & Environmental Science, Stanford engineers show that when metal oxide solar cells grow hotter, the photons are converted into electrons more efficiently. The opposite happens to silicon solar cells, which is they lose their efficiency as temperatures rise up.

"We've shown that inexpensive, abundant and readily processed metal oxides could become better producers of electricity than was previously supposed," Chueh said.

The unexpected discovery of Stanford engineers will change the way we produce, store and consume energy, especially solar energy.

Before the results of the Stanford's team's discovery, water-splitting has been deemed impractical due to cost. Silicon-based solar cells are good at converting visible and ultraviolet light into electricity, but they waste infrared light. It was believed that metal oxides became less efficient when they grow hotter, but the results of the experiment showed the opposite.

"Standard cells utilize a relatively small portion of the spectrum, and the rest is lost as heat," Chueh said.


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